Numerical study on abnormal airflow patterns and particle deposition characteristics in the realistic HUA model with pharyngeal obstruction

Abstract

The effects of morphological variation of pharynx on abnormal airflow patterns and particle deposition characteristics in the realistic OSA HUA model with pharyngeal obstruction are numerically studied using the LES-DPM. Firstly, the LDA measurements on airflow patterns in the HUA model are executed to verify the reliability of LES, and the numerical simulations on particle deposition behaviors in a simplified human throat are conducted to validate the reliability of DPM. Afterwards, the airflow patterns, including velocity field, pressure field and shear stress field, and the regional/total particle deposition features with various particle sizes (0.5–10 μm) at different respiration intensities (16.8–60 L/min) inside HUA model are examined. The fitting formula among total deposition efficiency, particle size and respiratory intensity is eventually established. The results lead to the following conclusions: (1) The morphological variation of pharynx significantly affects the abnormal airflow patterns and particle deposition features. Pharyngeal obstruction not only induces abnormal high intensity of turbulent flow, negative pressure and positive shear stress, but also causes abnormal high local deposition efficiency in the nasal cavity and larynx. (2) The enhancement of respiration intensity greatly aggravates the abnormal airflow patterns. With the increasing of respiration intensity, the jet-flow, reversed-flow, negative pressure and positive shear stress all noticeably strengthen. Rapid medical diagnosis on airway operation can be realized by judging the maximal negative pressure and positive shear stress. (3) The increments of both particle size and respiration intensity evidently augment the abnormal particle deposition features. With the rising of particle size and respiration intensity, the total particle deposition efficiencies obviously improve. However, inertial impaction is the essential mechanism for abnormal deposition characteristics, which is more important than that of turbulence intensity. This work not only would help to understand the pathophysiology of OSA disease, but also would assess both the health impacts of inhaled particles and the therapeutic efficacy of inhaled drug aerosols in the airways of OSA patients.